Expansible-fluid turbine.



B. S. OHURGH & A. B. COX.

} EXPANSIBLE FLUID TURBINE.

APPLICATION FILED 001'. 29, 1909.

3 SHEETS-SHEET 2.

Patented Oct. 28, 1913.

INVENTORS WITNESSES g WM H f w 0 MC .V, R M n 5M m mm m M M 4 MAB coLumnm PLANDGRAPII c0., WASHINGTON, n. c.

B. S. CHURCH & A. B. COX.

EXPANSIBLE FLUID TURBINE.

APPLIGATION FILED OCT. 29,1909.

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ATTORNEY COLUMBI{\ PLANOCIRAP" CO-. WASHINGTON. D. c.

stratus PATENT OFFICE.

BENJAMIN S. CHURCH, 0]? NEW Yfll'tl l, AND ABRJMIKAM B. 80X, 01? CHERRY VALLEY, NEW YORK.

EXPANSIBLE-FLUID TURBINE.

1 b all whom it may, concern Specification of Letters Patent.

Application filed Qctcber 2 9, 1809.

Be it known that We, BENJAMlN Sui Iliiuuon, of the borough of l rlanhattan, city,

county, and State of New York, and Anna,- HAM E. Cox, of the town of Cherry Valley, county of ()tsego, and State of New York, F have invented certain new and useful Improvements in lCXpansible-Fluid Turbines, j of which the follow ng 1s a full, complete,

and exact description, reference beinghad to the accompanying drawings, which are hereby made part thereof.

The ob1ect of our invention is to dev se a l l l l lifatented Got. 28, 1913.

Serial No. 525,339.

sure over a large number of successive stages. 'lhn-dly, upon the density or specific volume oi the ex Jansible fluid. As re- V ciprocating' engine to th same extent as at turbine more particularly for the use of 2 superheated se to the use of other expansible fluids which am, although Well adapted present. It is t.

u" therefore that an cxpausible fluid o'l:

great specific volume can be utilized, the proportion of clearance leakshall be simple in design, and less subject to leakage losses than is the case with existing expahsible l'luid turbines.

One of the chief losses in ei'liciency in existing elcpansible fluid turbines resides in the clearance leakage, to obviate which it is generally necessary in turbines of the pressure stage type, most prominently exemplified by the Parson turbine, to make the clearances as small as is mechanically practicable. Even then there enough clearance leakage loss to increase very considerably What theoretically should be the duty or consumption of the turbine.

The object of our invention is to minimize this clearance leakage, and for such purpose to utilize a very simple mechanical construction, the spirit of which is capable of being embodied in many forms of turbines, although shown only in connection With the turbine invented by B. Church, and described in United States Letters Patent, hlmuber 878,118. Such application of our invention will be apparent to any skilled in the art of turbine construction and design.

The clearance leakage loss in a turbine depends upon several conditions: Firstly, upon the mechanical smallness of the clearance which reduced as much is mechanically practicable in view of the varying co-eiiicients of thermal expansion and the rigidity of the materials of which the turbine is composed. Secondly, upon the pressure tending to force the fluid through the ::learance, which can be reduced by subdividing the ma..i1num difl erenc in pres age can be much diminished; but it is not 1 economical from a thermodynamic point of view to use only low pressure or vacuum saturated steam, because the thermal energy of such steam comparatively small; it, however fun of comparatively low pressure be superheated, its density can be diminished and its thermal energy increased to that of high pressure st am, or even better, and the clearance leakage in a turbine using such steam will be proportionally as small as that of a vacuum turbine, while the thermodynamic e'lliciency can be made to exceed that oi the best piston engine using high pressure steam. The reason for this that the thermodynamic etliciency ot the low pressure siuperheated stean i canbe made to equal that of high pressure steam, and the turbii'le using the attenuated superheated low pressure steam ivill show the Well known e'lliciency of the vacuum or exhaust steam turbine. It would seem that while high pressure saturated steam is well adapted for use in a piston eng ac, and very low vacuum steam is not, owing to the limited capacity of the cylinders, and while the exact reverse is ordinarily true of the turbine, a turbine can be constructed posse ing the advantages of both, by the utilization of superheated steam of comparatively low pressure.

In Figure 1 is shown a mathematical table illustrating the manner in which a turbine for the use of superheated steam is to be constructed. The table is explained as tollo u's: To begin with it is as. uined that sat- 1 never have become the competitor of the rea urated steam of 131.49 pounds pressure absolute is generated in the boiler. This pressure was chosen arbitrarily being in the neighborhood of 115 pounds gage, which is a boiler pressure quite commonly used. Saturated steam of 131.49 pounds pressure has a temperature of 348 degrees Fahrenheit. For the purpose of the table it is assumed that 100 degrees of superheat is added. This would make the temperature of the steam 148 degrees, as is shown in column 2 of the table opposite to stage 1. Columns 1 and 18 of the table are arbitrarily chosen for the purposes of the table, and depend upon the amount of subdivision of pressure and temperature necessary to produce the requisite steam jet velocity in view of the speed of rotation for which the turbine is designed. In the Church turbine illustrated, it is dcsired to have a uniform steam jet velocity at every stage, though it will be clearly apparent that in other forms of turbine construction the steam jets might well be of varying velocities, particularly if the steam flow be continuously radial, without departing from the spirit of the table. To estimate the amount of thermal energy necessary to produce a uniform steam jet velocity of 500 feet per second, as shown in column 11 the formula V==(2g,7l\1 ll") is used; that is V== (64.4X1X778 X5) 500.055,

where a unit weight of steam is taken, 778 is the mechanical equivalent of heat and g:32.2. It will then be clear that the unit weightone pound of steam must part with 5 B. T. U. of thermal energy at every stage in order to develop a uniform steam jet velocity of 500 feet per second, it being assumed that this jet velocity is transmitted to the blades of the turbine and otherwise dissipated except in so far as the small velocity of approach is concerned. Column 9 gives the specific heat of superheated steam at varying degrees of superheat, which has been determined by several well known experimenters. It will therefore be clear that if 5 be divided by the specific heats given in column 9 the decrease in temperature from stage to stage in column 10 will be obtained. hese are then subtracted successively to give the temperatures of the superheated steam in column 2. The specific heats in column 9 correspond to the temperatures in column 2 and the mathematical process of obtaining column 2 is cyclical, that is, it consists of first dividing E- by .564 and obtaining 8.87 then subtracting 8.87 from 4:48 and obtaining 139.13 (stage 2), then taking the specific heat of 91.93 degrees of superheat column 3; which quantity 91.93 is obtained by subtracting from 139.13 the temperature of Saturated steam at the pressure of 130.18 (stage 2). The pressures in column 1 and the volumes in column 8 are determined by the use of the empirical formula,

where T is the temperature given in column 2. This process is continued with the degree of superheat of the steam gradually diminishing, as shown in column 3 until the saturation point is reached as shown on the table by the double line. Column 5 is to be particularly noted. It gives the difference of pressure P,P from stage to stage and will be seen to be comparatively small, much smaller than in column 5 which gives the successive differences of pressure of the saturated steam. In column 8 the volume of steam at 4148 degrees temperature and 131.49 pounds absolute pressure is approximately 1 cubic feet per pound weight of steam; a pound of saturated steam at this temperature would require a pressure of almost 100 pounds per square inch and would be in volume not more than 1 cubic foot, while the thermodynamic efficiency in either case would be approximately equal, no argument is required to demonstrate the practical advantages accruing from the use of the low pressure superheated steam; in particular, the great reduction in clearance leakage, to say nothing on the other hand of the practically unworkable boiler pressure of the saturated steam.

If the steam jets be assumed to move at a certain velocity, the size of the ports or nozzles can be easily obtained mathematically by a process of division, consequently column 12 is obtained in this manner from columns 8, 8 and 11; if there are four ports in each stage, as in the construction illustrated, and the nozzles chosen be two inches wide the successive dimensions given in column 13 are obtained by dividing the quantities given in column 12, by the numher 8there being four ports, each two inches wide. In measuring the nozzles along the circumference of a circle, as in the con struction illustrated the angle of inclination must be considered; this circumferential length is given in columns 14; and 15.

In the saturated part of the table columns 2 4 and 6 are obtained from the steam tables. The fall in temperature in column 2 is such that 5 B. T. U. of thermal energy is transformed into kinetic energy at each stage. This quantity, 5 B. T. U., is obtained by an averaging process, assuming that an equal amount of energy is developed by a uniform drop of 4 in temperature at each stage as shown in column 1O except as affects stage 14, which divergence will be orena-e subsequentlyexplained, which while not absolutely true is su'lheiently correct tor practieal purposes. The formula is used to calculate the amount oi thermal energy developed for a given fall of te1nperature.

lolumn 7, which the condition of the steam, or its percentage of dryness, is obtained by the empirical formula Column 8 is obtained by multiplying column (3 by column 7, and the rest of the table is similarly obtained for both the superheated and saturated steam. Column 16 shows an allowance in the lower stages of steam leakage from the upper stages in the cmistruction illustrated. Column 17 makes allowance for guide vanes, which are necessary in the large lower stage ports or nozzles.

Particular emphasis is to be laid on the fact that in the superheated part of the table the quantities given in column 8 are all approximatel l cubic feet. With diminishing temperature, superheated steam contracts in volume, and does not espaml. as is the case with saturated steam; and it the fall in temperature and the diminution in pressure bear themutual relatioi'lship shown in the table, the volume of a unitwcight of superheated steam can be kept constant, and all the ports and nozzles are consequently of the same i'uniorin size in the superheated position otthe turbine.

There is some uncertainty as to what the exact specific heat of steam superheated only a few degrees above the saturation point; this is indicated by the irregularity in the fall of ten'iperature in column 11 at stages l-el and 15; but it will be noted by observing columns I l and 15 that the transition from ports of a uniformsize to those of an increasing cross-section begins very gradually, which would logically point to a very practical solution of what is probably the only uncertain element in the computation. lit may be possible that the exact specific heat of siuverheated steam has not been evaluated closely enough for such a computation as this, but, granted that such is the case, it would seem very practical to provide merely a sullicient number of ports or non zles of uniform cross-section, and to use more or less otthem as results would indieate. The logic of such a method of procedure will be clear upon reasonable con sideration of the various columns in the upper part oi? the table.

l i e believe that the construction of a turbins for the use of superheated steam having steam ports, nozzles, or passages of uniform and shape, is broadly new, and we desire to claim this feature as completely as possible.

The maimer of applying our invention to the Church turbine is illustrated in Figs. 2 and 3 in which S is the shaft which rotates in the bearings B B and carries the wheel disk D which on its periphery is supplied with the bucket blades Z), 7). Fig. 2 is a view partly in section taken along the line KX of Fig, 3. Fig. 3 is a section taken vertically along the line 21 Z ol l ig. In Fig. 52 only a certain number oi the blades are shown for the sake of simplicity. The superheated steam enters through the inlet .l which is Y-shaped and conveys the steam to both sides of the turbine. stitutes practically a separate turbine, this arrangement being chosen to elin'iinate thrust. It will therefore sull'ice to describe one side only. The inlet I is omitted in Fig. 2, but it will be clear that the steam traverses the path shown by the solid arrow in Fig. 3 into the chamber 0, from which it passes downward and outward through the small ports just below a gainst the blades Z), Z), and into the chambers 2, 2 (Fig. 2) which correspond with the stage similarly indicated on Fig. .1. From these chambers the steam passes upward as indicated by the dotted arrow in Fig. 3 and between the partitions indicated by the dotted lines in Fig, 2, into the chambers indicated by C (Fig. 2) from which it passes through the corresponding nozzles, against the blades 7), l) and into the chambers 3, 3 and so on, until it finally reaches the chamber 3st and passes from the exhaust into another turbine, or series o'l? turbines, designed to carry the process down into the proper degree of vacuum. The table shown in llig. 1 does not show how the principles described are applied to turbines using a vacuum, but the application is so zupparent and clear that it would seem amply sullieient merely to refer to it.

The bearings B are in the form of sleeves or bushings and are supplied with keys K1, 7a to keep them from turning with the shaft. They have spherical exterior bearing surfaces which fitaccurately into rings r r and are loosely enough supported so as to turn longitudinally, and thereby to prevent all. binding upon the shaft by reason of strain or heat distortion of the easing. The rings r r are held by the hub castings ll lal which rest upon then frames A A and inclose the wheel disk D. Lhey also carry the side ozistings F F which in turn siiipport the cover plate cast iugs J J .he center casting l) is held between the side castings l3 F and is pro-- vided with a suitable web to stiffen it. The portrings P P are su iported by the hub castings H H and also by the side Each side concastings F F and contain the successive ports or nozzles which are too small to ad mit of being numbered without confusing the figures, but the construction of which is readily apparent.

The bucket blades Z), Z) are not shown as having any clearance with the parts surrounding them. The clearance is so small as not to well admit of illustration, but are such as is generally used between the motor and the casing of a turbine. he disk is also supplied with a labyrinth Q, to prevent leakage of steam into the center of the casing. In practice a. certain proportion of steam leaks in from the upper stage chambers and passes out into the lower stage chamber of the turbine casing. To prevent this steam from escaping into the outer air and being wasted thereby, the stuffing boxes V V. are provided.

W'hile the thrust is practically balanced, there being a clear passage for the steam from one side to the other at every chamber all around the casing there is still some danger of chattering on the part of the motor. To avoid damage to the blades the innermost ring of the labyrinth Q. is made to clear the casing by a smaller amount than the ends of the blades, so that the ring shall strike the casing first. As this striking would give rise to unnecessary friction, the shaft is provided with the thrust collar U held between the adjustable thrust rings T T which are supported by the frame A and retained in position by the set nuts or collars N. The frame A is not in. any way connected with the rest of the machine, except that it is supported on the same base M, and consequently it is not liable to be distorted by the heat and pressure affecting the other parts.

It will be noted that the turbine mechanism shown is provided with only 34k successive chambers for 34: stages, while the table shown as Fig. 1 calls for a l stage As the figures are merely illustrative of the table this is not considered material, because it would, except in very small sizes generally be inadvisable to run through the entire range of temperature and pressure with a single turbine only.

Exactly where and 1 how the range of pressure and temperature i is to be divided up is a question for the desi 'ner, and does not affect the principle involved, which, is that the cross-section of each of the successive nozzles is obtained by the process outlined in the table, and that the nozzles in the superheated portion of the turbine are all of the same, or approximately the same cross-section. It will be quite clearly apparent that the mathematical process described can be equally well applied to a turbine of the Parsons type by spacing and proportioning the rows of bladesin the part designed to receive the superheated steam so they shall be exactly alike, and gradually, or at intervals increasing the size of the blades for this expanding saturated steam as in existing machines. The same can be said of all other multiple stage types of turbines and would seem so obvious as not to require illustration.

Having now fully and completely described our invention, what we desire particularly to claim is:

1. A steam turbine having steam passages through which the steam passes at a uniform velocity, part of said passages being of uniform dimensions, and intended to confine the steam while in a superheated condition, and the remaining passages of gradually increasing dimensions for the expanding saturated steam.

2. A turbine for superheated steam having part of its steam passages of uniform size and shape, and part of its steam passages of gradually increasing size and similar shape.

3. A turbine for superheated steam having chambers and nozzles through which the steam passes successively, part of which nozzles are of uniform size and shape, and the remainder of gradually increasing dimensions.

A turbine for superheated steam having chambers and nozzles through which the steam passes at a calculated velocity, part of which nozzles are of uniform dimensions for the superheated steam, and the remain der of gradually increasing dimensions for the expanding saturated steam.

BENJAMIN S. CHURCH. ABRAHAM B. COX. Vitnesses Annxaxnnn MOFFAT, JOSIAH L. BLaoKwnLL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

